First thing: The anti-malware programs that claim to remove snap.do ARE FAKE (mainly). Do you have anything that seems shady or not supposed to be on your PC? If so, remove it (especially the programs developed by ReSoft Ltd, the creators of snap.do). That is only half of your problems gone.
You want to go to Settings under Tools, then go to Set Pages on Startup. Snap.do could or should be there. If so, press the 'X' next to it and set Google to launch on startup.
After that, click on 'Manage Search Engines' under 'Search'. If snap.do is on either 'Other search engines' or 'Default search engines', delete it.
If it still redirects to snap.do when you go on a New Tab, you want search for a Chrome Extension called New Tab Redirect. With this, you can set it to where you want it to redirect to. When you have installed this, set it to redirect to Google (optional, can make it redirect to other sites too). I would also recommend putting on an AdBlocker and Ghostery.
If you have any LEGITIMATE internet security (Malwarebytes and Spybot - Search and Destroy is recommended), run a scan and see if it comes up.
Hope I helped. -Chromatose